Question 184561
Let x be the side of the square.


The new rectangle has sides x + 8 (twice) and x – 2 (twice).


Therefore the perimeter = 2(x + 8) + 2(x – 2) = 4x + 12.


Now 4x + 12 = 40; therefore 4x = 28; x = 7.


The length of a side of the square is 7 cm.